Featured Research

from universities, journals, and other organizations

Antarctic Ice Sheet unstable at end of last ice age

Date:

May 28, 2014

Source:

Oregon State University

Summary:

A new study has found that the Antarctic Ice Sheet began melting about 5,000 years earlier than previously thought coming out of the last ice age -- and that shrinkage of the vast ice sheet accelerated during eight distinct episodes, causing rapid sea level rise.

A new study has found that the Antarctic Ice Sheet began melting about 5,000 years earlier than previously thought coming out of the last ice age -- and that shrinkage of the vast ice sheet accelerated during eight distinct episodes, causing rapid sea level rise.

Related Articles

The international study, funded in part by the National Science Foundation, is particularly important coming on the heels of recent studies that suggest destabilization of part of the West Antarctic Ice Sheet has begun.

Results of this latest study are being published this week in the journal Nature. It was conducted by researchers at University of Cologne, Oregon State University, the Alfred-Wegener-Institute, University of Hawaii at Manoa, University of Lapland, University of New South Wales, and University of Bonn.

The researchers examined two sediment cores from the Scotia Sea between Antarctica and South America that contained "iceberg-rafted debris" that had been scraped off Antarctica by moving ice and deposited via icebergs into the sea. As the icebergs melted, they dropped the minerals into the seafloor sediments, giving scientists a glimpse at the past behavior of the Antarctic Ice Sheet.

Periods of rapid increases in iceberg-rafted debris suggest that more icebergs were being released by the Antarctic Ice Sheet. The researchers discovered increased amounts of debris during eight separate episodes beginning as early as 20,000 years ago, and continuing until 9,000 years ago.

The melting of the Antarctic Ice Sheet wasn't thought to have started, however, until 14,000 years ago.

"Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last ice age, that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size," said lead author Michael Weber, a scientist from the University of Cologne in Germany.

"The sediment record suggests a different pattern -- one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation," Weber added.

The research also provides the first solid evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of very rapid sea level rise that began some 14,500 years ago, according to Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.

The largest of the eight episodic pulses outlined in the new Nature study coincides with meltwater pulse 1A.

"During that time, the sea level on a global basis rose about 50 feet in just 350 years -- or about 20 times faster than sea level rise over the last century," noted Clark, a professor in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "We don't yet know what triggered these eight episodes or pulses, but it appears that once the melting of the ice sheet began it was amplified by physical processes."

The researchers suspect that a feedback mechanism may have accelerated the melting, possibly by changing ocean circulation that brought warmer water to the Antarctic subsurface, according to co-author Axel Timmermann, a climate researcher at the University of Hawaii at Manoa.

Some 9,000 years ago, the episodic pulses of melting stopped, the researchers say.

"Just as we are unsure of what triggered these eight pulses," Clark said, "we don't know why they stopped. Perhaps the sheet ran out of ice that was vulnerable to the physical changes that were taking place. However, our new results suggest that the Antarctic Ice Sheet is more unstable than previously considered."

Today, the annual calving of icebergs from Antarctic represents more than half of the annual loss of mass of the Antarctic Ice Sheet -- an estimated 1,300 to 2,000 gigatons (a gigaton is a billion tons). Some of these giant icebergs are longer than 18 kilometers.

More From ScienceDaily

More Earth & Climate News

Featured Research

Mar. 31, 2015 — Soil organic matter, long thought to be a semi-permanent storehouse for ancient carbon, may be much more vulnerable to climate change than previously thought. Scientists have found that the common ... full story

Mar. 31, 2015 — The ocean is a large reservoir of dissolved organic molecules, and many of these molecules are stable against microbial utilization for hundreds to thousands of years. They contain a similar amount ... full story

Mar. 31, 2015 — Using the assessment tool ForWarn, US Forest Service researchers can monitor the growth and development of vegetation that signals winter's end and the awakening of a new growing season. Now these ... full story

Mar. 31, 2015 — Geoscientists have revealed information about how continents were generated on Earth more than 2.5 billion years ago -- and how those processes have continued within the last 70 million years to ... full story

Mar. 31, 2015 — Until now electric fences and trenches have proved to be the most effective way of protecting farms and villages from night time raids by hungry elephants. But researchers think they may have come up ... full story

Mar. 31, 2015 — The volcanologist Stephen Self, an expert on super-eruptions, was the first modern-day scientist to visit Tambora in Indonesia, the site of the largest volcanic eruption in 1,000 years. On the 200th ... full story

Mar. 31, 2015 — Researchers have detected a human fingerprint deep in the Borneo rainforest in Southeast Asia. Cold winds blowing from the north carry industrial pollutants from East Asia to the equator, with ... full story

Mar. 31, 2015 — Landfills can make a profit from all their rotting waste and a new patent explains exactly how to make the most out of the stinky garbage sites. Decomposing trash produces methane, a landfill gas ... full story

Mar. 31, 2015 — As the five-year anniversary of the explosion of the Deepwater Horizon oil rig approaches, a new report looks at how twenty species of wildlife are faring in the aftermath of the ... full story

Mar. 31, 2015 — Accurately anticipating an approaching typhoon's destructive force makes all the difference in advance preparations and as a consequence, the cost in lives. But over the decades, climate scientists ... full story

Related Stories

Jan. 8, 2015 — The balmy islands of Seychelles couldn't feel farther from Antarctica, but their fossil corals could reveal much about the fate of polar ice sheets. About 125,000 years ago, the average global ... full story

Aug. 31, 2014 — A new study of satellite data from the last 19 years reveals that fresh water from melting glaciers has caused the sea level around the coast of Antarctica to rise by 2cm more than the global average ... full story

Oct. 6, 2013 — Scientists have discovered huge ice channels beneath a floating ice shelf in Antarctica. At 250 meters high, the channels are almost as tall as the Eiffel tower and stretch hundreds of kilometers ... full story

Feb. 11, 2011 — A set of maps has illustrated, for the first time, how the last British ice sheet shrunk during the Ice Age. Experts developed the maps to understand what effect the current shrinking of ice sheets ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.